diff --git a/ckanext/versioned_datastore/lib/downloads/download.py b/ckanext/versioned_datastore/lib/downloads/download.py
index 123295e..4a3f38e 100644
--- a/ckanext/versioned_datastore/lib/downloads/download.py
+++ b/ckanext/versioned_datastore/lib/downloads/download.py
@@ -519,7 +519,7 @@ def generate_derivative(self):
                             filename = os.path.extsep.join([resource_id, fileext])
                         shutil.copy2(filepath, os.path.join(temp_dir, filename))
                     else:
-                        raise NotImplemented(
+                        raise NotImplementedError(
                             f'No raw file is available for resource {resource_id}'
                         )